1. Field of the Invention
The present invention relates to an air bag cover opening mechanism for use in a vehicle. Description of the Related Art:
A technique concerning a structure for fixing an air bag cover for a passenger seat air bag is disclosed in Japanese Utility Model Application Laid-Open No. 63-111353.
This technique is shown in FIG. 6. The prior art discloses, as shown in FIG. 6, an opening 9 for allowing an unillustrated air bag to jump out therethrough which is provided at a predetermined location in an instrument panel 8 corresponding to a passenger seat. The opening 9 is closed by an air bag cover 2. The air bag cover 2 has an upper end secured rotatably to the instrument panel 8 via a hinge or the like, and a lower end secured to the instrument panel 8 by means of resin-made retainers 3 and bolts 4, 41.
A detailed description will now be given of a specific prior art structure for securing the lower end of the air bag cover 2.
As shown in FIG. 7, the air bag cover 2 has a three-layered structure comprising a metal insert 21, a foamed layer 22, and a surface layer 23. A notched portion 25 to which the retainers 3 is attached is not provided in the foamed layer 22 or the surface layer 23 but is provided only in the insert 21, and a threaded hole 24 is also provided therein.
The retainer 3 is arranged such that two retaining portions 31a, 32a are connected to each other via a thin integral hinge 33, as shown in FIG. 8.
One retaining portion 31a is provided with a slot 34 extending longitudinally from a thicknesswise central portion of one end thereof. Also, a hole 35 is provided in a central portion of the retaining portion 31a in such a manner as to penetrate the two slotted segments thereof. Grooves 36 are respectively formed longitudinally in opposite sides of the other retaining portion 32a, and a hole 37a is provided in a central portion thereof in such a manner as to penetrate the same in the same direction as the hole 35.
As shown in FIG. 8, the retainer 3 is fitted to the notched portion 25 in such a manner that the slot 34 of the retaining portion 31a is received by the innermost portion of the insert 21, while the grooves 36 of the other retainer 32a are received by inner lateral portions of the insert 21 at the notched portion 25. Thus the overall retainer 3 is accommodated in the notched portion 25. Then, one retaining portion 31a is secured to the air bag cover 2 as the screw 41 is inserted into the holes 35, 24 and tightened. Meanwhile, the other retaining portion 32a is superposed on a fixing portion 81 of the instrument panel 8, and is secured to the instrument panel 8 by a bolt 4 inserted into the hole 37a provided in the other retaining portion 32a. As a result, the air bag cover 2 is secured to the instrument panel 8.
With the above-described structure for fixing the air bag cover, since the retainer 3 is closely secured to the air bag cover, even if vibrations are applied to the instrument panel 8 during normal running of the vehicle, the integral hinge 33 does not undergo fatigue. At the time of inflation of the air bag, however, the air bag cover 2 is pressed by a load caused by the inflation of the air bag, with the result that the integral hinge 33 is broken, thereby allowing the air bag cover 2 to be pushed open.
However, with the above-described conventional structure for fixing the air bag cover 2, since the other retaining portion 32a secured to the instrument panel 8 side of the retainer 3 is constantly located at the same position relative to the movement of the air bag cover 2 which is pushed open toward the interior of the vehicle compartment, both a load oriented in the pulling direction and a load oriented in the shearing direction act on the integral hinge 33 which is the breaking portion. Accordingly, the load occurring at the time of the inflation of the air bag is not effectively transmitted to the integral hinge 33 which is the breaking portion of the retainer 3, with the result that there is the possibility that the air bag cover 2 may not be pushed open smoothly.